Ice detection system for a gas turbine

ABSTRACT

To prevent ice from clogging a trash screen disposed in an air supply duct for a gas turbine, a conduit is disposed in communication with the duct downstream of the trash screen and has a pivotally mounted screen cooperatively associated with a spring and a switch so that the switch closes and initiates operation of an auxiliary heater disposed in the duct when ice begins to form on the pivotally mounted screen.

United States Patent Bennett et a1.

[ 1 ICE DETECTION SYSTEM FOR A GAS TURBINE Inventors: Alan D. Bennett, Essington, Pa.;

Robert C. Farkas, Anchorage, Alaska [73] Assignee: Westinghouse Electric Corporation,

Pittsburgh, Pa.

Filed: Sept. 25, 1972 Appl. No.: 292,239

U.S. Cl. 219/201, 60/3909 D Int. Cl. l H05b 1/00 Field of Search 219/201; 60/3909 D;

244/134 D, 134 R; ZOO/81.9

[56] References Cited UNITED STATES PATENTS 2,705,866 4/1955 Quinby et a1. 1. 60/3909 D [451 Mar. 12, 1974 2,469,375 5/1949 Flagle 244/134 R X 2,711,453 6/1955 Leigh, Jr.... 60/3909 D 3,058,305 10/1962 Leigh, Jr.... 60/3909 D 2,744,992 5/1956 Spears 60/3909 D Primary ExaminerC. L. Albritton Attorney, Agent, or Firm--Fred J. Baehr, Jr.

14 Claims, 4 Drawing Figures PATENIED NAB I 2 I974 FIGZ ICE DETECTION SYSTEM FOR A GAS TURBINE BACKGROUND OF THE INVENTION This invention relates to gas turbines and more particularly to a system for detecting the buildup of ice on a trash screen before the ice clogs the screen.

Under certain atmospheric conditions ice, ice fog or snow, hereinafter referred to as ice, will form on a trash screen disposed in an air intake duct of a gas turbine, shutting off the air to the turbine and rendering it inoperative. Once the ice has formed it is very difficult to melt, however, if the buildup of ice is detected as it begins to form, auxiliary heaters in the inlet of the air sup ply duct can be made operative to prevent the formation of ice and melt the small quantity thereof which may have already formed.

Systems which analyze the ambient air condition to detect when the atmosphere conditions are predisposed to the formation of ice have been utilized, how ever, such systems are expensive.

SUMMARY OF THE INVENTION In general, a gas turbine, when made in accordance with this invention, comprises a compressor portion, an inlet duct supplying ambient air to the compressor, a grate cooperatively associated with the duct to prevent trash from entering the compressor, means for heating the ambient air disposed upstream of the grate and means disposed in communication with the duct for sensing the buildup of ice on the grate due to ambient air condition and for initiating the operation of the heating means upon sensing the ice buildup.

BRIEF DESCRIPTION OF THE DRAWINGS The objects and advantages of this invention will become more apparent from reading the following detailed description in connection with the accompanying drawings, in which:

FIG. I is a plan view of a gas turbine incorporating an ice detection system made in accordance with this invention;

FIG. 2 is an enlarged elevational view of the ice detector;

FIG. 3 is an enlarged elevational view ofa heater for the ice detector;

FIG. 4 is a circuit diagram for the ice detection and heating system.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings in detail, FIG. 1 shows a gas turbine 1 having a compressor portion 3 and a supply duct 5 supplying ambient air to the compressor 3. The duct 5 comprises a silencer portion 7 and a transition portion 9 disposed downstream of the silencer portion 7. A trash screen, grate 11 or other partial obstruction is cooperatively associated with the duct 5 to prevent trash or other foreign material from entering the compressor 3 and is disposed in the upstream end of the transition portion 9 of the duct 5.

An air heater 13 is disposed adjacent the inlet end of the duct 5 and has an auxiliary burner 14 or other means disposed therein to heat the influent air. An ice detecting system 15 or means for sensing the buildup of ice on the trash screen is disposed in the transition portion of the duct 5 downstream of the trash screen 11.

As shown in FIG. 2, the ice detection system comprises a conduit 17 in fluid communication with the transition portion 9 of the duct 5 and with ambient air. A screen 19 is transversely disposed within the conduit 17 and is pivotally mounted or hinged so as to swing axially within the conduit so that the screen 19 is in one position when no ice is formed thereon and is in a second position when ice begins to build up thereon. A spring 21 is cooperatively associated with the pivotally mounted screen 19 and biases it in a direction counter to the flow of air therethrough or towards the first position. A switch 23 is also cooperatively associated with the screen 19 and is disposed to be open when the screen 19 is in its first position and to be closed when the screen 19 is in its second position.

As shown in FIG. 3, the ice detection also includes means for heating the air entering the conduit 17. The heating means comprises an enclosure or box 25 disposed on the inlet end of the conduit 17. The enclosure 25 has a divider plate 27 disposed to form two compartments 29 and 31. One compartment 29 contains the inlet end of the conduit 17 and has openings 33 therein allowing ambient air to enter the compartment. The other compartment 31 has a blower 35, a space heater 39, and a plurality of openings 41 disposed therein. The blower 35 has a discharge nozzle 47, which extends through the divider plate 27, and a heating coil 49 is disposed within the discharge nozzle 47, so that warm air can be provided to the inlet of the conduit 17 to melt ice formed on the pivotally mounted screen 19.

The space heater 39 warms the compartment 31 containing the blower 35 to prevent ice from forming on the inlet of the blower 35.

FIG. 4 shows a circuit diagram for the deicing system in which electrical energy is supplied to the system via lines L and L and a ground or neutral conductor or line G. Conductors 61, 63 and 65 are connected in parallel across line L and the ground conductor G. The switch 23 is disposed in conduit 61 in series with a coil 67C ofa relay 67R. Contacts 670 of the relay 67R close when the relay 67R is energized to provide a signal, which initiates the operation of the heater 13. Normally open contacts 67b of the relay 67R are disposed in the conductor 63 in series with a' motor 69M of a timer 69T. Contacts 69a of the timer 69T close when the motor 69M is energized, locking in the relay 67R viz conductor 70 for a predetermined time interval. Contacts 69b are disposed in the conductor 65 and are connected in series with a coil 71C of a starter 718. The coil 71C is energized for a predetermined time interval commencing with the motor 69M being energized. This second mentioned time interval is much shorter, in the range of one-third that of the first mentioned time interval, allowing the ice formed on the pivotally mounted screen to melt and reform if the conditions for forming ice persist. Contacts 71a and b are connected in series with lines L and L and a motor 35M of the blower 35 to the heating coil 49, which is disposed in parallel with the motor 35M. Energizing the motor 35M and heater coil 49 when the coil 71C of the starter 718 is energized. The space heater 49 is disposed in series with a thermostatically controlled switch 75 in a conductor 77 connected across lines L and L and is energized when the temperature within the enclosure drops below a predetermined value.

The operation of the deicing system is as follows: Ambient air flowing through the conduit 17 passes across the pivotally mounted screen 19, which is held in one position by the bias of the spring 21, and as the atmospheric conditions approach a condition where ice would begin to form on the trash screen 1 1, because of the exaggerated conditions in the conduit 17, ice begins to form on the pivotally mounted screen 19. As the ice forms on the pivotally mounted screen 19, the pressure drop across the screen builds up and increases until the screen swings to its other position, closing the switch 23 and sending a signal to commence operation of the air heater 13. The timing motor 69M is also energized, energizing the starter 715, which starts the motor 35M of the blower 35 and energizes the heating coil 49 so that the blower 35 blows hot air into the compartment 29 and into the inlet of the conduit 17 to melt the ice formed on the pivotally mounted screen 19. As the ice melts the pressure drop across the pivotally mounted screen 19 is reduced allowing the screen to return to its first position and the switch 23 to open. After a longer interval of time, approximately three times the original .time interval, the contacts 67a open. If ice has not reformed on the screen 19 the relay 67R trips out opening the circuit to the timer 69T and shutting down the air heater 13. The system then remains inoperative until ice again begins to form on the pivotally mounted screen 19 which again initiates the cycle. If on the other hand, ice has reformed on the pivotally mounted screen 19 the timer 69T begins the heating cycle to melt the ice formed on the pivotally mounted screen 19 and the air heater 13 remains operable during the continuation of the cycle.

The ice detecting system, hereinbefore described, advantageously exaggerates the condition existing at the trash screen 11 so that ice will form on the pivotally mounted screen 19 before it begins to form on the trash screen 11 providing a warning of the approach of an icing condition prior to its actually occurring on the trash screen 11 or on the compressor inlet guide vanes, thus providing a system which prevents ice from building up rather than a system which melts the ice after it has formed. Experience has shown that preventing the formation of ice is far superior to a system which melts the ice once it is formed, as the latter system requires a greater quantity of heat and a much longer period of time and the machine will operate inefficiently during the time that the intake is partially blocked by ice.

What is claimed is:

1. A gas turbine comprising a compressor portion, an inlet duct supplying ambient air to said compressor, a grate cooperatively associated with said duct to prevent trash from entering the compressor, means for heating said ambient air disposed upstream of said grate and means disposed in communication with said duct for sensing a condition indicative of a buildup of ice on said grate due to ambient air conditions and for initiating the operation of said heating means upon sensing a condition indicative of an ice buildup, said sensing means comprising a conduit in fluid communication with the duct downstream of the grate and in fluid communication with ambient air, and means disposed within said conduit responsive to the ambient air conditions to indicate a predisposition to the buildup of ice on the grate and to initiate operation of the heating means, and means for heating the air entering said conduit, said conduit air heating means being operable for a predetermined interval after initiation of the operation of the first mentioned heating means.

2. A gas turbine as set forth in claim 1, wherein the conduit heating means comprises a heating coil disposed to heat the air entering the conduit.

3. A gasturbine as set forth in claim 2, wherein the conduit heating means further comprises a blower having an air outlet disposed to blow air across the heating coil and into the inlet end of the conduit.

4. A gas turbine as set forth in claim 3, wherein the conduit heating means further comprises an enclosure for the blower and the conduit, said enclosure having a heating element disposed therein to prevent ice from building up on the inlet of the blower.

5. A gas turbine comprising a compressor portion, an inlet duct supplying ambient air to said compressor, a grate cooperatively associated with said duct to prevent trash from entering the compressor, means for heating said ambient air disposed upstream of said grate and means disposed in communication with said duct for sensing a condition indicative of a buildup of ice on said grate due to ambient air conditions and for initiating the operation of said heating means upon sensing a condition indicative of an ice buildup, said sensing means comprising a conduit in fluid communication with the duct downstream of the grate and in fluid communication with ambient air, and means disposed within said conduit responsive to the ambient air conditions to indicate a predisposition to the buildup of ice on the grate and to initiate operation of the heating means, said means disposed within the conduit responsive to the buildup of ice due to ambient air conditions comprising a screen transversely disposed within the conduit and means for initiating a signal when the ice builds up on said screen.

6. A gas trubine as set forth in claim 5, wherein the screen is pivotally mounted and has bias means cooperatively associated therewith to hold the screen in a first position when there is no ice buildup thereon and to allow the screen to move to a second position when there is an ice buildup thereon.

7. A gas turbine as set forth in claim 6, wherein the means for initiating the signal when the ice builds up on the screen is a switch operated by the movement of the screen from its first to its second position.

8. An ice sensing device for an ambient air supply duct having a partial obstruction disposed therein to prevent foreign material from entering the duct and means for heating said ambient air disposed upstream of said partial obstruction, said ice sensing device comprising a conduit in fluid communication with said duct downstream of said partial obstruction and in fluid communication with said ambient air, means disposed in said conduit responsive to the ambient air conditions to indicate a predisposition to the buildup of ice on said partial obstruction and to initiate operation of the heating means, and means for heating the air entering said conduit, said conduit air heating means being operable for a predetermined interval after initiation of the operacross the heating coil and into the inlet end of the conduit.

11. An ice sensing device as set forth in claim 10, wherein the conduit heating means further comprises an enclosure for the blower and the inlet end of the conduit, said enclosure having a heating element disposed therein to prevent ice from building up on the inlet of the blower.

12. An ice sensing device for an ambient air supply duct having a partial obstruction disposed therein to prevent foreign material from entering the duct and means for heating said ambient air disposed upstream of said partial obstruction, said ice sensing device comprising a conduit in fluid communication with said duct downstream of said partial obstruction and in fluid communication with said ambient air, and means disposed in said conduit responsive to the ambient air conditions to indicate a predisposition to the buildup of ice on said partial obstruction and to initiate operation of the heating means, said means disposed within the conduit responsive to the predisposition of ice build up comprising ascreen transversely disposed within the conduit and means for initiating a signal when ice builds up on the screen.

13. An ice sensing device as set forth in claim 12, wherein the screen is pivotally mounted and has bias means cooperatively associated therewith to hold the screen in a first position when there is no ice buildup and to allow it to move to a second position when there is an ice buildup thereon.

14. An ice sensing device as set forth in claim 13, wherein the means for initiating the signal when the ice builds up on the screen is a switch operable by the movement of the screen from its first to its second positlon. 

1. A gas turbine comprising a compressor portion, an inlet duct supplying ambient air to said compressor, a grate cooperatively associated with said duct to prevent trash from entering the compressor, means for heating said ambient air disposed upstream of said grate and means disposed in communication with said duct for sensing a condition indicative of a buildup of ice on said grate due to ambient air conditions and for initiating the operation of said heating means upon sensing a condition indicative of an ice buildup, said sensing means comprising a conduit in fluid communication with the duct downstream of the grate and in fluid communication with ambient air, and means disposed within said conduit responsive to the ambient air conditions to indicate a predisposition to the buildup of ice on the grate and to initiate operation of the heating means, and means for heating the air entering said conduit, said conduit air heating means being operable for a predetermined interval after initiation of the operation of the first mentioned heating means.
 2. A gas turbine as set forth in claim 1, wherein the conduit heating means comprises a heating coil disposed to heat the air entering the conduit.
 3. A gas turbine as set forth in claim 2, wherein the conduit heating means further comprises a blower having an air outlet disposed to blow air across the heating coil and into the inlet end of the conduit.
 4. A gas turbine as set forth in claim 3, wherein the conduit heating means further comprises an enclosure for the blower and the conduit, said enclosure having a heating element disposed therein to prevent ice from building up on the inlet of the blower.
 5. A gas turbine comprising a compressor portion, an inlet duct supplying ambient air to said compressor, a grate cooperatively associatEd with said duct to prevent trash from entering the compressor, means for heating said ambient air disposed upstream of said grate and means disposed in communication with said duct for sensing a condition indicative of a buildup of ice on said grate due to ambient air conditions and for initiating the operation of said heating means upon sensing a condition indicative of an ice buildup, said sensing means comprising a conduit in fluid communication with the duct downstream of the grate and in fluid communication with ambient air, and means disposed within said conduit responsive to the ambient air conditions to indicate a predisposition to the buildup of ice on the grate and to initiate operation of the heating means, said means disposed within the conduit responsive to the buildup of ice due to ambient air conditions comprising a screen transversely disposed within the conduit and means for initiating a signal when the ice builds up on said screen.
 6. A gas trubine as set forth in claim 5, wherein the screen is pivotally mounted and has bias means cooperatively associated therewith to hold the screen in a first position when there is no ice buildup thereon and to allow the screen to move to a second position when there is an ice buildup thereon.
 7. A gas turbine as set forth in claim 6, wherein the means for initiating the signal when the ice builds up on the screen is a switch operated by the movement of the screen from its first to its second position.
 8. An ice sensing device for an ambient air supply duct having a partial obstruction disposed therein to prevent foreign material from entering the duct and means for heating said ambient air disposed upstream of said partial obstruction, said ice sensing device comprising a conduit in fluid communication with said duct downstream of said partial obstruction and in fluid communication with said ambient air, means disposed in said conduit responsive to the ambient air conditions to indicate a predisposition to the buildup of ice on said partial obstruction and to initiate operation of the heating means, and means for heating the air entering said conduit, said conduit air heating means being operable for a predetermined interval after initiation of the operation of said first mentioned heating means.
 9. An ice sensing device as set forth in claim 8, wherein the conduit heating means comprises a heating coil disposed to heat the air entering the conduit.
 10. An ice sensing device as set forth in claim 9, wherein the conduit heating means further comprises a blower having an air outlet disposed to blow air across the heating coil and into the inlet end of the conduit.
 11. An ice sensing device as set forth in claim 10, wherein the conduit heating means further comprises an enclosure for the blower and the inlet end of the conduit, said enclosure having a heating element disposed therein to prevent ice from building up on the inlet of the blower.
 12. An ice sensing device for an ambient air supply duct having a partial obstruction disposed therein to prevent foreign material from entering the duct and means for heating said ambient air disposed upstream of said partial obstruction, said ice sensing device comprising a conduit in fluid communication with said duct downstream of said partial obstruction and in fluid communication with said ambient air, and means disposed in said conduit responsive to the ambient air conditions to indicate a predisposition to the buildup of ice on said partial obstruction and to initiate operation of the heating means, said means disposed within the conduit responsive to the predisposition of ice build up comprising a screen transversely disposed within the conduit and means for initiating a signal when ice builds up on the screen.
 13. An ice sensing device as set forth in claim 12, wherein the screen is pivotally mounted and has bias means cooperatively associated therewith to hold the screen in a first position when there is no ice buildup and to allow it to move to a second pOsition when there is an ice buildup thereon.
 14. An ice sensing device as set forth in claim 13, wherein the means for initiating the signal when the ice builds up on the screen is a switch operable by the movement of the screen from its first to its second position. 